1. Field of the Invention
This invention relates to a heating medium and a use of the same. More particularly, this invention relates to a heating medium comprising powdered aluminum and powdered calcium oxide in a specific blending ratio and a method of using the heating medium by contacting it with water. The heating medium of this invention is useful to an apparatus requiring temperatures of approximately 100.degree. C. for at least 20 minutes, for example, a heating apparatus of a heating cooking container of a food for emergency or a field ration.
2. Description of the Prior Art
In recent years, there has been increased the use of a food which is heated and warmed in situ by means of a heating apparatus built in a heating cooking container in which a food for emergency, a liquid food such as sake and so on or various kinds of field rations such as lunch and so on are contained in the heating cooking container.
As one of the heating apparatus has been proposed a various kinds of heating apparatus making use of exothermic reaction of a chemical compound, which are roughly classified into three types, one is a type making use of addition reaction of water to an oxide, the other is a type making use of reaction of a metal with an acid, and another is a type making use of addition reaction of water to anhydrous salt.
The Japanese Food Sanitation Law provides that an apparatus and a food packing container which are used in business should be clean and be in sanitary conditions (Article 8) and that an apparatus and a food packing container which contain harmful and poisonous substances and have a bad influence on human health by coming into contact with a food should not be used (Article 9). Therefore, the types making use of the reaction of a metal with an acid or addition reaction of water to magnesium-iron alloy have been considered to be preferable because of generation of a peculiar smell. It is considered that this is true also in other countries than Japan.
In addition to the regulation of the Food Sanitation Law, there are some requirements for the field ration which is heated and warmed in situ as a portable food or field ration. That is to say, it should be right and compact. Accordingly, the weight and/or bulk of the heating cooking container should not be extremely increased by incorporating the heating apparatus into the heating cooking container. And furthermore, the heating apparatus should generate heat for a short time by simple operation at any time everywhere a wearer goes.
For reasons as stated above, that is to say, for the regulation of the Food Sanitation Law, right weight and compact, simplicity of operation, efficiency and so the type making use of heat of addition reaction of water to calcium oxide takes up the mainstream of a heating medium built in the heating cooking container.
By the way, there are various kinds of form and bulk for the heating cooking container, that is, approximately 200 cm.sup.3 at the minimum and approximately 2000 cm.sup.3 at the maximum. The inventor of this invention carried out fact-finding on the time at the maximum required from opening of a portable food to finish of eating or drinking with respect to "sake" the bulk of which is relatively small and a box lunch sold at a railroad station the bulk of which is relatively large, as a result, we have found it was approximately 20 minutes.
And we have found that a portable box lunch or food should be heated at approximately 90.degree. C. and above in order to heat and warm it completely depending on contents therein. Since the heat capacity of a material of the heat cooking container itself is low, insulating effectiveness can not be expected to the heat cooking container itself. And furthermore, we have found that the heating medium used in the heating apparatus itself has to give rise to exothermic reaction to arrive at the maximum temperature and has effect on maximizing the time required for lowering at least to a room temperature from the maximum temperature, that is to say, temperature retention time.
As stated previously, the type making use of heat of addition reaction of water to calcium oxide has token up the mainstream of a heating medium built in the heating cooking container. While the heating medium making use of heat of addition reaction of water to calcium oxide fulfills the requirements of the Japanese Food Sanitation Law, it is required that a large quantity of calcium oxide is used in order to arrive at 90.degree. C. and above immediately after reaction which is maintained for at least 20 minutes because calorific value of the reaction of water with calcium oxide is small, which causes increase in the weight and bulk of the heat cooking container.